The overall goal of this project is to explore the role of T and B lymphocytes in the pathogenesis and prevention of IDDM in NOD mice. Basically, our prior studies have shown that IDDm in NOD mice results from shifts in the balance between autoaggressive T cells and cells that regulate their activity or present their effector action bet cells. This project will explore the role of CD8 T cells in the initiation of the diabetic process. We have isolated and cloned CD8 T cells that appear early in these mice; depletion of CD8 T cells at 2-4 weeks is known to prevent diabetes. Using these cloned T cells, we plan to pursue the following specific aims: 1. We will prepare mice transgenic for the T cell receptor, in order to study their maturation, activation, and effector functions. 2. We will identify their beta cell specific antigen using hybrids engineered for sensitive detection of cDA encoding the antigenic peptide. We will determine the mechanism of homing of these cells to the islets, which happens in the first three hours after injection. 4. We believe that CD4 T cells are only activated once the CD8 cells have released autoantigens, and we believe that B cells play a critical role in the diversification that occur after this event. This is because beta-deficient NOD mice do not develop diabetes. We will explore the role of beta cells in diabetes by using NOD mice lacking beta cells or by blocking the CD40 ligand which is necessary for conferring co-stimulatory activity on these cells. Eventually, we hope our analysis will provide clues that will allow us to prevent diabetes using insulin using insulin injection, as we have evidence that an insulin-specific T cell can block adoptive transfer and spontaneous disease in our mice.